Economic Implementation of 99.98% Efficiency in Natural-Cooling Modular MVDC SSCBs

Abstract

This paper presents a modular medium voltage direct-current (MVDC) solid-state circuit breaker (SSCB) with high efficiency. The presented design method is modularity oriented, which includes thermal analysis of conduction cell, busbar design of conduction disk, and structure design of conduction tower. The implementation includes both continuous current conduction and fault current interruption. This paper includes three major contributions. First, it presents an economic analysis in terms of efficiency and cost as the design guideline for the main conduction configuration of SSCBs. Second, it provides a complete modular SSCB design procedure, showing both parallel and cascade scalability. Third, this paper investigates the effect of main conduction path stray resistances on SSCB efficiency and power loss. A medium-voltage SSCB prototype rated at 4kV/100A are experimentally implemented. The power density achieves 26.2 kW/L. The continuous conduction tests are conducted at 100A for 1hour, the steady-state efficiency achieves 99.98% with maximum temperature of 37°C. The fault interruption tests are successfully conducted at 4 kV/ 137A and 4 kV/ 1 kA with different system inertia.